Why does 1995 gmc safari knock when driving from back of van

need to check rear end, tire, u-joints and brakes its one of those more then likely. hope this helps

Rotation in rear tire is hitting. Go underneath rotor to fix

actually safaris are primarily rear driven vehicles If your hearing a knocking from the back of the van its either a bad u joint in the drive axel or a bad bearing in the rear dif. But im willing to bet your drive axel has a bad u joint crawl under it and shake it if its solid its not a u joint but 99% of my money says it is. This is not a winter job unless you have a heated garage but relatively easy to fix all you need is a 10m socket and a hammer, and needle nose pliers or a pointy screwdriver to take the c clips out.